<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>button</title>
  <style>
    .pink{
      background-color: pink;
    }

  </style>
</head>
<body>
<button class="pink">按钮1</button>
<button>按钮2</button>
<button>按钮3</button>
<button>按钮4</button>
<script>
    let bts=document.querySelectorAll('button')
    for ( i = 0; i < bts.length; i++) {
        bts[i].addEventListener('click',function (){
            document.querySelector('.pink').className=''
            this.className='pink'
        })

    }
</script>
</body>
</html>
